1. Field of the Invention
The present invention relates to improvements of control circuits such as a one chip microcomputer in which an analog circuit is formed on the same chip.
2. Description of the Related Art
A control circuit (microcomputer) on which an analog circuit including an operation control section to perform a digital operation and additionally, for example, an operation amplifier on the same chip is mounted has been used in various fields. The present applicant has proposed a microcomputer in which an analog circuit for exclusive use in a camera is built in, for example, in Jpn. Pat. Appln. KOKAI Publication No. 11-142722.
Moreover, an auto focus (AF) camera has heretofore been developed by which a light is projected onto a subject and a reflected signal light is detected to judge whether a subject is far or near, so that automatic focusing is possible in accordance with a result of the judgment. Moreover, a technique for inexpensively constituting basic functions in the camera is known in the above-described publication. In this technique, for example, a distance-measuring circuit for performing AF is constituted on the same chip as that of the microcomputer of a sequence controller of the camera.
Furthermore, the microcomputer has also been used in merchandises for consumers, such as various electric products and portable apparatuses. Accordingly, complicated operations or sequence controls based on operation inputs by users or detection results by sensors, further controls of displays or actuators, and the like can easily be carried out in accordance with predetermined programs.
In recent years, there has also been a microcomputer in which, in addition to a timer and a pulse generator, the control of the display (e.g., LCD), and peripheral circuits such as an A/D conversion circuit and a D/A conversion circuit are efficiently built in the chip. Since this microcomputer can similarly be used in different products, cost reduction has been advance because of a mass production effect. For example, the above-described chip for use in the control is also used for remote controllers and household electric appliances.
Moreover, with respect to an improvement in the above-described operation amplifier, a technique has been proposed in Jpn. Pat. Appln. KOKAI Publication No. 6-260851 in which a switch changeover function is disposed in an input section of the operation amplifier to perform an offset correction.